1. Field of the Invention
The present invention generally relates to communication quality acquisition apparatuses and methods employed in cellular mobile communication systems using spread signals such as CDMA(Code Division Multiple Access), and more specifically, to an apparatus and a method for acquiring communication quality through the CDMA pilot channel in the service area.
2. Description of the Related Art
In the prior art communication method that divides a given band into several channels and then conducts communications through such channels, the communication quality is affected by thermal noise caused by decrease in receiving power and interference noise in the co-channel and adjacent channels caused by the reuse of spatially the co-channel and adjacent channels. Then, its communication quality is identified by measuring the receiving power of the channel sent from the operating base station. Such receiving power can be measured by extracting the signal spectrum in each desired channel by the use of frequency converters and frequency selection filters and then measuring the power provided from each filter.
However, in the case of the CDMA method, which is regarded as the most promising one among the future mobile communication methods, the acquisition of communication quality in the service area should be conducted in a different way.
In the CDMA method, since the allocated band is not divided into several channels but shared by all the communication channels, those channels are distinguished from each other with different codes. Therefore, in order to receive signals in a given channel for the acquisition of communication quality, the code assigned to each channel must be identified and synchronization must be established by detecting the code interval. Because a number of channels are required to be measured at the same time for the acquisition of communication quality, a parallel data processing is necessary for code synchronization. Further, since the CDMA method improves communication quality by using a wide band, the delay profile, which is two-dimensional data, must be acquired for the acquisition of communication quality. Then, the CDMA method poses such problems that its data processing becomes very complicated when implementing code synchronization over a number of channels to acquire communication quality and that the amount of data increases along with the acquisition of delay profile.
Delay during code synchronization causes failed data acquisition and thus lowers the code synchronization accuracy. It also leads to a problem of extended “measurement window”, which is the time interval for the measurement of delay profile. As a result, the amount of data processing grows during measurement and the portion of meaningful data in the acquired data decreases. In addition, such an increase in the data amount caused by the acquisition of delay profile shortens the meaning data acquisition time, thus lowering the processing efficiency.